1. Field of the Invention
The invention is directed to an improved magnet valve of the type used, for example, in hydraulic fluid systems.
2. Description of the Prior Art
A conventional magnet valve, in particular for a hydraulic unit, which is used for instance in an antilock brake system (ABS) or a traction control system (TCS) or an electronic stability program system (ESP system), is shown in FIG. 1. As can be seen from FIG. 1, besides a magnet unit 5 with a cover disk 12, the conventional magnet valve 20, which is open when without current, includes a valve cartridge that in turn includes a capsule 6, a valve insert 1, a tappet 2, a restoring spring 3, and an armature 7. In the production of the magnet valve 20, the capsule 6 and the valve insert 1 of the valve cartridge are joined together by pressing, and by means of a sealing weld 8, the valve cartridge is sealed off hydraulically from the atmosphere. In addition, the valve insert 1 absorbs the pressure forces that occur in the hydraulic system and carries them via a calked flange 9 to a calking region, not shown, on a fluid block. In addition, the valve insert 1 receives the so-called valve body 4, which includes a valve seat 10 into which the tappet 2 plunges in sealing fashion, in order to perform the sealing function of the magnet valve 20. The tappet 2 includes an axial guide face 2.1, a spring guide 2.2, onto which the restoring spring 3 is slipped and guided radially inward in the short region of the spring guide 2.2, a tappet cone 2.3, a transition region 2.4, and a tappet dome 2.5, which plunges in sealing fashion into the valve insert 1. As also seen from FIG. 1, the tappet 2 and the restoring spring 3 are guided in the valve insert 1; the tappet 2 is guided in a tappet guide 11, and the restoring spring 3 is guided radially from inside and centered on one end on the spring guide 2.2 of the tappet 2 and rests on the first contact face 2.1 of the tappet 2, and on the other end rests, axially guided, on the valve body 4 on a second contact face 4.1. No provision for further fixation or centering of the restoring spring 3 at its installation site is provided. The flow path of the fluid through the magnet valve extends via the restoring spring 3, so that the spring force of the restoring spring 3 is operative in the region of the flow forces which because of the flow are capable of acting on the turns of the restoring spring 3. If the order of magnitude of the spring force and the order of magnitude of the stiffness of the restoring spring 3 are within the range of the forces of the flow acting on the spring turns, then an unwanted influence on the spring behavior can occur from the flow. Hence the restoring spring 3 may for instance lift from its contact with the valve body 4, which may be associated with a corresponding (force) action on the valve tappet 2 and an unwanted influence on the valve function. Moreover, the unguided portion of restoring spring can be laterally deflected or shifted, so that contact and hence frictional forces can occur between the valve insert 1 and the tappet 2. Because of the frictional forces generated, the valve behavior can be adversely affected, and the tappet 2 may be damaged by the spring ends, which may have burrs on them.